Analyzing fluids in core samples contained in pressurized nmr core holders with 1h and 19f nmr

ABSTRACT

Pressure coring where the core apparatus drills the core sample and seals the core sample at its native downhole pressure (e.g., several thousand psi) may be expanded to include nuclear magnetic resonance (NMR) imaging components to produce a pressurized NMR core holder that allows for NMR imaging of the core samples having been maintained in a downhole fluid saturation state. NMR imaging performed may include 1H and also 19F imaging depending on the chamber fluid used in the pressurized NMR core holder.

BACKGROUND

The present application relates to analyzing core samples with nuclearmagnetic resonance (NMR) imaging, relaxometry, and diffusimetry.

Often samples of subterranean formations referred to as core samples areacquired via core drilling methods. The core samples are then analyzedto determine the properties (e.g., porosity, hydrocarbon content, watercontent, organic matter content, mineralogy content including shalecontent, pore structure content, and the like) of the portion of theformation from which they were acquired.

In order to analyze core samples from a subterranean formation, a coreapparatus drills a core sample. Once at the surface, the core sample isoften preserved by hermetically sealing the core sample in a thickcoating of wax or by freezing with dry ice. The purpose of preservationis primarily to maintain the core and any fluids therein and thedistribution of those fluids in the core sample as close as possible toreservoir conditions. However, as the native pressure of the core sampleis invariably much higher than the pressure at the surface, the gasesand light fluids that may have been trapped in the rock will escape fromthe core sample as it is brought to the surface thus making the coresample less accurate in providing a picture of the subterraneanformation from which the core sample was taken.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of theembodiments, and should not be viewed as exclusive embodiments. Thesubject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIG. 1 illustrates an example system for collecting core samples andstoring the core samples in a pressurized NMR core holder.

FIGS. 2A and 2B illustrate a cross-sectional side view andcross-sectional top view of a portion of a pressurized NMR core holder.

FIG. 3 illustrates a partial cross-sectional side view of a portion of apressurized NMR core holder.

FIG. 4 illustrates an NMR analysis device with a pressurized NMR coreholder therein.

DETAILED DESCRIPTION

The present application relates to analyzing core samples with nuclearmagnetic resonance (NMR) imaging, relaxometry, and diffusimetry whilethe core samples are contained in a pressurized NMR core holder.

The methods of the present disclosure expand on pressure coring wherethe core apparatus drills the core sample and seals the core sample atits native downhole pressure (e.g., several thousand psi). Pressurecoring mitigates the escape of pressurized gases and more effectivelymaintains the core sample in its native state for analysis. The methodsof the present disclosure integrate NMR capabilities with the pressurecoring.

To briefly describe the hardware for implementing the methods of thepresent application, the pressurized NMR core holders described herein,and variations thereof, may be used in conjunction with a coring devicedownhole. For example, FIG. 1 shows an example system 100 for collectingcore samples and storing the core samples in a pressurized NMR coreholder. In FIG. 1, a coring tool 102 is placed in a wellbore 104penetrating a subterranean formation 106 by a conveyance, illustrated asa wireline 108 conveyance. The coring tool 102 includes a pressurizedNMR core holder 110 described herein. In certain example embodiments,the coring tool 102 is placed in the wellbore 104 by another conveyance(e.g., coil tubing, wired coiled tubing, slickline, and the like) thatis connectable to the surface.

One skilled in the art would recognize the variations of the system 100that may be employed when performing the methods described herein. Forexample, the system 100 may be implemented with a portion of thewellbore 104 that is off-vertical (e.g., deviated or horizontal).

FIGS. 2A and 2B illustrate a cross-sectional side view andcross-sectional top view of a portion of a pressurized NMR core holder210. The pressurized NMR core holder 210 includes a housing 212 that iscapable of containing downhole fluid pressures. A coil holder 214 linesthe inside of the housing 212 and maintains one or more NMR coils 216 inposition. Each end 218,220 of the NMR coil 216 is connected to adifferent wire 222,224 that allows for connection to a control system226.

The control system 226 may be a singular system outside the pressurizedNMR core holder 210. For example, the pressurized NMR core holder 210may include connections that can be used to connect to the controlsystem 226 for NMR measurements. Alternatively, a portion of the controlsystem 226 (e.g., capacitors) may be mounted inside the pressurized NMRcore holder 210 and then coupled to the remainder of the control system226 for NMR measurements.

A core chamber 228 is defined by the coil holder 214 and the housing 212and is where the core sample 230 is placed. The pressurized NMR coreholder 210 may be sufficiently sized to hold between one and twenty coresamples 230.

Generally, the core samples 230 are stored in the pressurize NMR coreholder 210 to effectively maintain the reservoir fluids in the coresample in a downhole fluid saturation state. As used herein, the term“downhole fluid saturation state” refers to a state where at least 75%of the fluid in the core sample 230 present when collecting the coresample 230 is maintained in the core sample 230. To achieve a downholefluid saturation state, the pressurize NMR core holder 210 may maintaina temperature and/or a pressure at or near the downhole collectionconditions. In some instances, the fluid pressure in the pressurize NMRcore holder 210 may be within about 25% or, more preferably, withinabout 10% of the fluid pressure the core sample 230 was collected fromthe formation at. In some instances, the temperature in the pressurizeNMR core holder 210 may be within about 25% or, more preferably, withinabout 10% of the temperature the core sample 230 was collected from theformation at. In some instances, both the temperature and fluid pressurein the pressurize NMR core holder 210 may independently be within about25% or, more preferably, within about 10% of the temperature and thefluid pressure the core sample 230 was collected from the formation at.

The pressurize NMR core holder 210 may include a cover at one or moreends of the pressurize NMR core holder 210 that can be selectively movedbetween (1) an open position, where the one or more core samples 230 areable to be inserted into the pressurize NMR core holder 210, and (2) aclosed position, where the pressurize NMR core holder 210 is sealed.Accordingly, a cover activation mechanism may be coupled to thepressurize NMR core holder 210 and operable to move the cover betweenthe closed position and the open position.

To maintain the core sample 230 at an elevated temperature, additionalthermal components may be added to the pressurized NMR core holder 210and/or a downhole tool the pressurized NMR core holder 210 is a part of.

Further, the core chamber 228 may be filled with a fluid 232 (alsoreferred to herein as a chamber fluid) (e.g., a non-reactive heavyweight fluid) that is suitable for applying positive pressure to thecore samples to mitigate fluids from coming out of the core samples,thereby retaining the core samples native state (or similar thereto) forthe later NMR measurements and analysis, as described further herein.

FIG. 3 illustrates a partial cross-sectional side view of a portion of apressurized NMR core holder 310. The illustrated portion of the NMR coilholder 310 includes six NMR coils 316 a-f in a coil holder 314 and ahousing 312. Each end 318 a-f,320 a-f of the NMR coils 316 a-f isconnected to wires 322,324, respectively. While FIG. 3 illustrates thewires 322,324 extending through the housing 312, one skilled in the artwould recognize that the housing 312 would include ports, seals, and thelike to connect wires 322,324 to a control system 326.

In some embodiments, a coring tool (e.g., as illustrated in FIG. 1 or avariation thereof) (e.g., a sidewall coring tool that extracts coresamples from the sidewall of a wellbore or a bottom-hole coring toolthat extracts core samples from the bottom of a wellbore) may collect orotherwise acquire core samples from one or more locations within thewellbore and stored in pressurized NMR core holder (e.g., as illustratedin FIG. 2A, FIG. 2B, FIG. 3, or a variation thereof).

As illustrated in FIG. 3, six core samples 330 a-f have been placed inthe core chamber 328 of the coil holder 314 at locations along thelength of the pressurized NMR core holder 310 corresponding to the sixNMR coils 316 a-f. The core chamber 328 further contains the fluid 332.Then, when retrieved from the wellbore, the pressurized NMR core holder310 may be connected to the control system 326 (or a portion thereof ifsome of the control system 326 is part of the pressurized NMR coreholder 310) and placed in a magnetic field for taking NMR measurements.

The magnetic field may be generated by a plurality of methods. Forexample, an electromagnet, a superconducting magnet, a permanent magnet,or a permanent magnet array (e.g., a Halbach array) may be used. Themagnets may encompass the pressurized NMR core holder. Alternatively,for permanent magnets, two plate magnets may be placed radially opposingeach other relative to the pressurized NMR core holder. Otherconfiguration of magnets can also be implemented to generate asubstantially uniform magnetic field inside the core sample volume.

The magnets may be configured to provide a magnetic field along thelength of the pressurized NMR core holder. Alternatively, a smallerlength magnet (e.g., corresponding to the length of one to a few of theNMR coils) may be used and moved along the pressurized NMR core holderwhen performing NMR measurements and analysis.

For example, FIG. 4 illustrates an NMR analysis device 434 with apressurized NMR core holder 410 therein. The NMR analysis device 434includes a holder 436 that maintains the pressurized NMR core holder 410in a desired position and a magnet 438. The illustrated magnet 438 is ona stand 440 that is longitudinally movable 442 along rails 444 of theNMR analysis device 434. As discussed above, the magnet 438 may be anappropriate length to provide a magnetic field for one to several of theNMR coils in the pressurized NMR core holder 410. The pressurized NMRcore holder 410 is further coupled to a control system 426.

In alternate embodiments, the NMR analysis device may include more thanone magnet that is longitudinally movable along the pressurized NMR coreholder. This may allow for having two different strength magnets forperforming different NMR measurements (e.g., on different atomic nuclei,different resolution measurements, or different sensitivitymeasurements).

The methods of the present disclosure integrate NMR capabilities withthe pressure coring using the foregoing pressurized NMR core holders andNMR analysis devices, and suitable variations thereof.

In the methods of the present application, the chamber fluid (e.g., thefluid 232 illustrated in FIGS. 2A and 2B and fluid 332 of FIG. 3) ispreferably high density, high viscosity, and high-temperature stablefluids with limited ability to solubilize water and provide electricalinsulation. Examples of chamber fluids may include, but are not limitedto, silicon oil, halogenated hydrocarbons (i.e., having at least one Hof the hydrocarbon substituted with a halogen), perhalogenatedhydrocarbons (i.e., having all H of the hydrocarbon substituted with ahalogen), and the like, and any combination thereof. Exemplaryhalogenated hydrocarbons and perhalogenated hydrocarbons may include,but are not limited to, polychlorinated biphenyls, perfluorocarbons,perchlorocarbons, and the like, and any combination thereof. Forexample, FLUORINERT™ ELECTRONIC LIQUID FC-40 is a fully-fluorinatedliquid available from 3M.

In some instances, a hydrogen-absent fluid (e.g., a perfluorocarbon or aperchlorocarbon) may be used as the chamber fluid to mitigate anycontributions of the chamber fluid to the 1H (hydrogen-1) NMRmeasurements.

In some embodiments, the chamber fluid may be a fluorinated compound,thereby allowing for the NMR analysis methods described herein toinclude not only 1H NMR measurements but also 19F (fluorine-19) NMRmeasurements. Unless otherwise specified, the term “NMR measurements”refers to generally to NMR measurements and may include only 1H NMRmeasurements, only 19F NMR measurements, or both 1H and 19F NMRmeasurements.

In some instances, the chamber fluid may include weighting agents orviscosifiers dispersed therein to increase the viscosity and density ofthe chamber fluid to mitigate the fluid in the core samples leaking intothe chamber fluid. For example, when using a perfluorocarbon chamberfluid, a perfluoropolymer may be used to viscosify the perfluorocarbonto provide for a hydrogen-absent chamber fluid and/or a fluorinatedchamber fluid. In another example, weighting agents like barite andgalena may be used to achieve a desired density of the chamber fluid,and the diameter of the weighting agents may be adjusted to achieve adesired viscosity of the chamber fluid.

The NMR analysis device may take NMR measurements of one or more coresamples collected from one or more locations within a wellbore andstored in the pressurized NMR core holder. For example, in someinstances, a coring tool having a pressurized NMR core holder may beretrieved from the wellbore after collecting one or more core samples,the pressurized NMR core holder removed from the coring tool, and thecore sample(s) contained in the pressurized NMR core holder analyzedwith the NMR analysis device separate from the coring tool.

The NMR measurements taken of the core sample may be analyzed todetermine a variety of properties of the core sample. For example, 1HNMR measurements may include, but are not limited to, spin-echointensity, Carr, Purcell, Meiboom and Gill (CPMG) echo train for T2(spin-spin) relaxation times, inversion recovery experiments orsaturation recovery experiments for T1 (spin-lattice) relaxation times,free-induction decay experiments, pulsed or constant gradient spin echoor stimulated echo experiments for relaxation time and fluiddiffusivity, variable echo time (TE) experiments, and the like, and anycombination thereof. Known methods may use the measurements describedabove to derive the properties of the core sample like porosity, movableand non-movable fluids, hydrocarbon fluid types and saturation,wettability, organic content, pore structure including pore sizedistribution, permeability, fracture and pore connectivity, and thelike, and any combination thereof.

It should be noted that deriving a property of the core sample is notnecessarily a singular number but rather may be presented in a varietyof ways. For example, a numerical range that represents an estimation ofthe property value for the portion of the formation from which the coresample were taken may be the output of deriving a property. In anotherexample, deriving a property may produce an image of the property forthe core sample. For instances, deriving the oil-to-water ratio may berepresented by an image illustrating the oil-to-water ratio at differentlocations in the core sample. As used herein, the term “image” may be a3-dimensional representation; a matrix, a graph, or other suitablemathematical representation that equates to the 3-dimensionalrepresentation or a portion thereof (e.g., a slice of the 3-dimensionalrepresentation); and the like.

In some instances, fluorine-containing fluids (with or, preferably,without hydrogen atoms) may be used as the chamber fluid and both 1H and19F NMR measurements may be taken of the core sample. Similar to 1H NMRmeasurements, 19F NMR measurements may include, but are not limited to,T1 (spin-lattice) signal intensity, T2 (spin-spin) signal intensity, T1relaxation times, and T2 relaxation times. Again, the properties of thecore sample like porosity, movable and non-movable fluids, hydrocarbonfluid types and saturation, wettability, organic content, pore structureincluding pore size distribution, permeability, fracture and poreconnectivity, and the like, and any combination thereof may be derivedfrom 1H and 19F NMR measurements. One skilled in the art will recognizehow to derive properties of the core samples from NMR measurements.

Further, by using the fluorine-containing fluid and conducting NMRimaging measurements, 1H and 19F NMR measurements may be converted toimage of the hydrogen-containing fluid and fluorine-containing fluid,respectively, by known methods. As used herein, the term “1H image”refers to an image of the 1H NMR measurements. As used herein, the term“19F image” refers to an image of the 19F NMR measurements.

In some embodiments, the porosity of the core sample may be derived byanalyzing the NMR signal of individual data points in the 1H and 19Fimages (e.g., voxels for 3-dimensional representations and n,m locationsin matrices).

Further, by comparing the 1H and 19F images, the extent of fluidinfiltration from the fluorine-containing fluid into the core sample maybe derived. For example, portion of the 1H and 19F images that overlapor portions of the 19F image that encroach where the 1H image indicatesthe boundaries of the core sample (e.g., assuming a cylindrical coresample corresponding to the 1H image) may indicate that portions of thecore sample have been infiltrated with the fluorine-containing fluid. Todiscern between infiltrated fluorine-containing fluid and a chip in thecore sample, the data points in the portions of the 19F image in thepresumed infiltration location may be compared the data points that areclearly fluorine-containing fluid. If the value of the data points(e.g., the value of the 19F NMR measurement) are similar for both (e.g.,within 80% of each other), then the presumed infiltration location islikely a chip or other defect in the core sample.

In some embodiments, the 1H and 19F NMR measurements for each data pointmay be individually calibrated against the 1H NMR measurement for waterand the 19F NMR measurement for the fluorine-containing fluid,respectively, which are referred to herein as calibrated 1H NMRmeasurements and calibrated 19F NMR measurements, respectively. As usedherein, the term “calibrated 1H image” refers to an image of thecalibrated 1H NMR measurements. As used herein, the term “calibrated 19Fimage” refers to an image of the calibrated 19F NMR measurements.

In some instances, analyzing the NMR measurements may involve summingthe calibrated 1H images and calibrated 19F images to yield thecollective intensities of each pixel of the images. This applies tocases when if the fluorine-containing fluid has invaded the core sampleunder investigation. In this approach, the boundary of the core plug canbe identified from the proton image. Within the same volume of the sameboundary, the 19F image intensities are analyzed either collectively orpixel by pixel. The porosity of the entire core sample volume isrepresented by the summation of the calibrated proton intensity and the19F intensities within the volume, or the intensities are computedpixel-by-pixel to yield a porosity distribution image inside the porousrock space. In some instances, analyzing the NMR measurements mayinvolve computing the calibrated 19F pixel intensity image correspondingto the pixels in the core sample volume to obtain thefluorine-containing fluid infiltration image into the core plug sample.In some instances, the infiltration image of the core plug sample mayinclude an overlay of the calibrated 1H image, where the latter definesthe volume boundary of core plug sample. The foregoing methods may beused on a variety of lithologies (i.e., rock types) that composesubterranean formations including, but not limited to, sandstone,limestone, dolostone, claystone, coal, shale, diatomite, and the like,and any combination thereof.

In some instances, carbonate lithologies like limestone and dolostoneare vuggy (i.e., contain cavities about 1 mm or larger in the rock). Intraditional core sample analysis, core samples are generally consideredcylindrical and porosity is determined by the amount ofwater/hydrocarbon in the core. However, because the capillary forces arelower in vugs, much of the native fluid therein may escape the coresample from surface vugs under traditional analysis conditions. Methodsdescribed herein allow for a more accurate estimation of the core size,which results in a more accurate porosity value. For example, in someembodiments, analyzing the NMR measurements may involve subtracting thedata points from the calibrated 19F image that have a calibrated 19F NMRmeasurement that is not approximately the same as (e.g., at least 20%more than or at least 20% less than) the calibrated 19F NMR measurementof the fluorine-containing fluid to yield a boundary image of the coresample where the negative space of the boundary image is an adjustedcore volume. Then, the calibrated 1H NMR measurements and the calibrated19F NMR measurements in the adjusted core volume may be analyzed by thevarious methods described herein to derive properties of the core sample(e.g., porosity, porosity images, infiltration images, and the like).

In some instances, the fluid pressure in the pressurized NMR core holdercontaining the core sample may be decreased in a controlled manner, forexample, with a regulating valve, over time where one or more of theanalysis methods described herein are performed at two or morepressures. By reducing fluid pressure and analyzing the core sample, therate and amount the different native fluids release from the core sample(e.g., gas, liquid hydrocarbons, water, and the like) may be derived,which may mimic the manner and order in which the formation will releasenative fluids during a production operation. For example, someembodiments may involve retrieving the pressurized NMR core holder fromthe wellbore containing the core samples at downhole fluid saturationstate and/or pressure conditions, maintaining the cores samples at thedownhole fluid saturation state and/or pressure conditions until aftercollecting first NMR measurements on the core samples, reducing a fluidpressure in the pressurized NMR core holder, and performing second NMRmeasurements on the core samples. Then, both the first and second NMRmeasurements may independently be analyzed by any of the methodsdescribed herein.

The properties of the core samples and fluids contained therein may beused when designing and executing stimulation operations and productionoperations. For example, by collecting and analyzing (by one or more ofthe methods described herein) core samples at different locations withinthe subterranean formation, zones may be identified with highconcentrations of hydrocarbons but low porosity, which may requireadditional stimulation (e.g., fracturing or acidizing). In anotherexample, zones may be identified with high concentrations of movablewater and be isolated during production operations so that hydrocarbonproduction is enhanced. In yet another example, zones may be identifiedthat release some hydrocarbons readily but have significant residualhydrocarbons, which lead an operator to produce the readily releasedhydrocarbons first and then stimulate the zone to enhance production ofthe residual hydrocarbons.

The processor and corresponding computer hardware used to implement thevarious illustrative blocks, modules, elements, components, methods, andalgorithms described herein may be configured to execute one or moresequences of instructions, programming stances, or code stored on anon-transitory, computer-readable medium (e.g., a non-transitory,tangible, computer-readable storage medium containing programinstructions that cause a computer system running the program ofinstructions to perform method steps or cause other components/tools toperform method steps described herein). The processor can be, forexample, a general purpose microprocessor, a microcontroller, a digitalsignal processor, an application specific integrated circuit, a fieldprogrammable gate array, a programmable logic device, a controller, astate machine, a gated logic, discrete hardware components, anartificial neural network, or any like suitable entity that can performcalculations or other manipulations of data. In some embodiments,computer hardware can further include elements such as, for example, amemory (e.g., random access memory (RAM), flash memory, read only memory(ROM), programmable read only memory (PROM), erasable programmable readonly memory (EPROM)), registers, hard disks, removable disks, CD-ROMS,DVDs, or any other like suitable storage device or medium.

Executable sequences described herein can be implemented with one ormore sequences of code contained in a memory. In some embodiments, suchcode can be read into the memory from another machine-readable medium.Execution of the sequences of instructions contained in the memory cancause a processor to perform the methods and analyses described herein.One or more processors in a multi-processing arrangement can also beemployed to execute instruction sequences in the memory. In addition,hard-wired circuitry can be used in place of or in combination withsoftware instructions to implement various embodiments described herein.Thus, the present embodiments are not limited to any specificcombination of hardware and/or software.

As used herein, a machine-readable medium will refer to any medium thatdirectly or indirectly provides instructions to a processor forexecution. A machine-readable medium can take on many forms including,for example, non-volatile media, volatile media, and transmission media.Non-volatile media can include, for example, optical and magnetic disks.Volatile media can include, for example, dynamic memory. Transmissionmedia can include, for example, coaxial cables, wire, fiber optics, andwires that form a bus. Common forms of machine-readable media caninclude, for example, floppy disks, flexible disks, hard disks, magnetictapes, other like magnetic media, CD-ROMs, DVDs, other like opticalmedia, punch cards, paper tapes and like physical media with patternedholes, RAM, ROM, PROM, EPROM, and flash EPROM.

For example, the processor described herein may be configured forcommunicating with the NMR coil and related hardware to cause the NMRmeasurements (e.g., produce RF signals with the NMR coil and detect RFsignals with the NMR coil from the core sample and fluid) and switchbetween the 1H operational mode and the 19F operational mode as needed.The processor may also be configured to perform the analyses andcomparisons described herein. Further, the processor may produce anoutput that corresponds to the NMR measurements or analyses thereof.

Embodiments described herein include, but are not limited to, EmbodimentA, Embodiment B, and Embodiment C.

Embodiment A is a method comprising: collecting one or more core samplesfrom a subterranean formation with a coring tool coupled to apressurized nuclear magnetic resonance (NMR) core holder; placing theone or more core samples in the pressurized NMR core holder comprisingone or more NMR coils and containing a fluid; retrieving the pressurizedNMR core holder from the subterranean formation where the one or morecore samples at a downhole fluid saturation state; performing 1H NMRmeasurements on at least one of the one or more core samples in thepressurized NMR core holder at the downhole fluid saturation state; andderiving one or more properties of the at least one of the one or morecore samples based on the 1H NMR measurements.

Embodiment A may optionally include one or more of the following:Element 1: wherein the fluid comprises one or more selected from thegroup consisting of a viscosifier and a weighting agent; Element 2:wherein the one or more properties of the at least one of the one ormore core samples is selected from the group consisting of porosity,movable and non-movable fluids, hydrocarbon fluid types and saturation,wettability, organic content, pore structure including pore sizedistribution, permeability, and fracture and pore connectivity; Element3: wherein the fluid is a hydrogen-absent fluid; Element 4: wherein thefluid comprise a fluorine-containing fluid and the method furthercomprises: performing 19F NMR measurements on the at least one of theone or more core samples at the downhole fluid saturation state; andderiving the one or more properties of the at least one of the one ormore core samples based on the 1H NMR measurements and the 19F NMRmeasurements; Element 5: Element 4 and wherein deriving the one or moreproperties of the at least one of the one or more core samplescomprises: producing a 1H image of the 1H NMR measurements; producing a19F image of the 19F NMR measurements; and comparing the 1H image andthe 19F image to derive where the fluorine-containing fluid hasinfiltrated the at least one of the one or more core samples; Element 6:Element 4 and wherein deriving the one or more properties of the atleast one of the one or more core samples comprises: calibrating the 1HNMR measurements to a 1H NMR measurement of water to produce calibrated1H NMR measurements; calibrating the 19F NMR measurements to a 19F NMRmeasurement of the fluorine-containing fluid to produce calibrated 19FNMR measurements; producing a calibrated 1H image of the calibrated 1HNMR measurements; and producing a calibrated 19F image of the calibrated19F NMR measurements; Element 7: Element 6 and wherein deriving the oneor more properties of the at least one of the one or more core samplesfurther comprises: summing the calibrated 1H image and the calibrated19F image; and deriving porosity of the at least one of the one or morecore samples therefrom; Element 8: Element 6 and wherein deriving theone or more properties of the at least one of the one or more coresamples further comprises: ensemble averaging data points of thecalibrated 1H image and data points of the calibrated 19F image; andderiving porosity of the at least one of the one or more core samplestherefrom; Element 9: Element 6 and wherein deriving the one or moreproperties of the at least one of the one or more core samples furthercomprises: subtracting data points of the calibrated 19F image having avalue within 20% of a value of the fluorine-containing fluid to yield aninfiltration image; Element 10: Element 6 and wherein deriving the oneor more properties of the at least one of the one or more core samplesfurther comprises: subtracting data points of the calibrated 19F imagehaving a value at least 20% greater than or at least 20% less than of avalue of the fluorine-containing fluid to yield a boundary image where anegative space of the boundary image is an adjusted core volume; andderiving the one or more properties of the at least one of the one ormore core samples based on the 1H NMR measurements and/or the 19F NMRmeasurements that fall within the adjusted core volume; Element 11:Element 10 and wherein the subterranean formation comprises a carbonatelithology; Element 12: wherein the fluid comprises aperfluorohydrocarbon and a perfluoropolymer; and Element 13: wherein the1H NMR measurements are first 1H NMR measurements and the method furthercomprises: reducing a fluid pressure in the pressurized NMR core holderto a reduced fluid pressure; and performing second 1H NMR measurementson the at least one of the one or more core samples in the pressurizedNMR core holder at the downhole fluid saturation state. By way ofnonlimiting examples, Embodiment A may include the followingcombinations: Element 1 in combination with one or more of Elements2-13; Element 2 in combination with one or more of Elements 3-13;Element 3 in combination with one or more of Elements 4-13; Element 4 incombination with Element 12 and optionally in further combination withElement 13 and/or one or more of Elements 5-11; Element 4 in combinationwith Element 6 and two or more of Elements 7-10 and optionally infurther combination with Element 11; and the like.

Embodiment B is a method comprising: collecting one or more core samplesfrom a subterranean formation with a coring tool coupled to apressurized nuclear magnetic resonance (NMR) core holder; placing theone or more core samples in the pressurized NMR core holder comprisingone or more NMR coils and containing a fluid comprising aperfluorocarbon; retrieving the pressurized NMR core holder from thesubterranean formation where the one or more core samples at a downholefluid saturation state; performing 1H NMR measurements and 19F NMRmeasurements on at least one of the one or more core samples in thepressurized NMR core holder at the downhole fluid saturation state; andderiving one or more properties of the at least one of the one or morecore samples based on the 1H NMR measurements and the 19F NMRmeasurements.

Embodiment B may optionally include one or more of the following:Element 1; Element 2; Element 5; Element 6; Element 7; Element 8;Element 9; Element 10; Element 11; Element 13; and Element 14: whereinthe fluid further comprises a viscosifier that comprises aperfluoropolymer. By way of nonlimiting examples, Embodiment B mayinclude the following combinations: Element 1 in combination with one ormore of Elements 2, 5-11, and 13-14; Element 2 in combination with oneor more of Elements 5-11 and 13-14; Element 6 in combination with two ormore of Elements 7-10 and optionally in further combination with Element11; Element 13 in combination with one or more of Elements 1-2, 5-11,and 14; Element 14 in combination with one or more of Elements 1-2,5-11, and 13; and the like.

Embodiment C is a method comprising: collecting one or more core samplesfrom a subterranean formation with a coring tool coupled to apressurized nuclear magnetic resonance (NMR) core holder; placing theone or more core samples in the pressurized NMR core holder comprisingone or more NMR coils and containing a fluid comprising aperfluorocarbon; retrieving the pressurized NMR core holder from thesubterranean formation where the one or more core samples at a downholefluid saturation state; performing 1H NMR measurements and 19F NMRmeasurements on at least one of the one or more core samples in thepressurized NMR core holder at the downhole fluid saturation state;calibrating the 1H NMR measurements to a 1H NMR measurement of water toproduce calibrated 1H NMR measurements; calibrating the 19F NMRmeasurements to a 19F NMR measurement of the fluorine-containing fluidto produce calibrated 19F NMR measurements; producing a calibrated 1Himage of the calibrated 1H NMR measurements; producing a calibrated 19Fimage of the calibrated 19F NMR measurements; and deriving one or moreproperties of the at least one of the one or more core samples based onthe calibrated 1H image and the calibrated 19F image, wherein the one ormore properties of the at least one of the one or more core samples isselected from the group consisting of porosity, movable and non-movablefluids, hydrocarbon fluid types and saturation, wettability, organiccontent, pore structure including pore size distribution, permeability,and fracture and pore connectivity.

Embodiment C may optionally include one or more of the following:Element 1; Element 7; Element 8; Element 9; Element 10; Element 11;Element 13; and Element 14. By way of nonlimiting examples, Embodiment Cmay include the following combinations: Element 1 in combination withone or more of Elements 7-11 and 13-14; two or more of Elements 7-10 incombination and optionally in further combination with Element 11;Element 13 in combination with one or more of Elements 1, 7-11, and 14;Element 14 in combination with one or more of Elements 1, 7-11, and 13;and the like.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the present specification and associated claims areto be understood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the embodiments of the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claim, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

One or more illustrative embodiments incorporating the inventionembodiments disclosed herein are presented herein. Not all features of aphysical implementation are described or shown in this application forthe sake of clarity. It is understood that in the development of aphysical embodiment incorporating the embodiments of the presentinvention, numerous implementation-specific decisions must be made toachieve the developer's goals, such as compliance with system-related,business-related, government-related and other constraints, which varyby implementation and from time to time. While a developer's effortsmight be time-consuming, such efforts would be, nevertheless, a routineundertaking for those of ordinary skill in the art and having benefit ofthis disclosure.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered,combined, or modified and all such variations are considered within thescope and spirit of the present invention. The invention illustrativelydisclosed herein suitably may be practiced in the absence of any elementthat is not specifically disclosed herein and/or any optional elementdisclosed herein. While compositions and methods are described in termsof “comprising,” “containing,” or “including” various components orsteps, the compositions and methods can also “consist essentially of” or“consist of” the various components and steps. All numbers and rangesdisclosed above may vary by some amount. Whenever a numerical range witha lower limit and an upper limit is disclosed, any number and anyincluded range falling within the range is specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues. Also, the terms in the claims have their plain, ordinary meaningunless otherwise explicitly and clearly defined by the patentee.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces.

Use of the phrase “at least one of” preceding a list with theconjunction “and” should not be treated as an exclusive list and shouldnot be construed as a list of categories with one item from eachcategory, unless specifically stated otherwise. A clause that recites“at least one of A, B, and C” can be infringed with only one of thelisted items, multiple of the listed items, and one or more of the itemsin the list and another item not listed.

As used herein, the term “or” is inclusive unless otherwise explicitlynoted. Thus, the phrase “at least one of A, B, or C” is satisfied by anyelement from the set {A, B, C} or any combination thereof, includingmultiples of any element.

The invention claimed is:
 1. A method comprising: collecting a set ofone or more core samples from a subterranean formation with a coringtool coupled to a pressurized nuclear magnetic resonance (NMR) coreholder; placing the set of core samples in the pressurized NMR coreholder comprising one or more NMR coils and containing a fluidcomprising a perfluorocarbon; retrieving the pressurized NMR core holderfrom the subterranean formation where the set of core samples is at adownhole fluid saturation state; performing NMR measurements on the setof core samples in the pressurized NMR core holder at the downhole fluidsaturation state, wherein performing the NMR measurements comprisesperforming at least one of 1H NMR measurements and 19F NMR measurements;and deriving one or more properties of the set of core samples based onthe NMR measurements.
 2. The method of claim 1, wherein the fluidcomprises one or more of a viscosifier and a weighting agent.
 3. Themethod of claim 2, wherein the viscosifier comprises a perfluoropolymer.4. The method of claim 1, wherein deriving the one or more properties ofthe set of core samples comprises: calibrating the 1H NMR measurementsto a 1H NMR measurement of water to produce calibrated 1H NMRmeasurements; and producing a calibrated 1H image of the calibrated 1HNMR measurements, wherein deriving one or more properties of the set ofcore samples is based on the calibrated 1H image.
 5. The method of claim1, wherein deriving the one or more properties of the set of coresamples comprises: calibrating the 19F NMR measurements to a 19F NMRmeasurement of a fluorine-containing fluid to produce calibrated 19F NMRmeasurements; and producing a calibrated 19F image of the calibrated 19FNMR measurements, wherein deriving one or more properties of the set ofcore samples is based on the calibrated 19F image.
 6. The method ofclaim 1, wherein the one or more properties of the set of core samplesis selected from the group consisting of porosity, movable andnon-movable fluids, hydrocarbon fluid types and saturation, wettability,organic content, pore structure including pore size distribution,permeability, and fracture and pore connectivity.
 7. The method of claim1, further comprising: reducing a fluid pressure in the pressurized NMRcore holder after performing the NMR measurements on the set of coresamples in the pressurized NMR core holder at the downhole fluidsaturation state; performing the NMR measurements on the set of coresamples in the pressurized NMR core holder at the reduced fluidpressure, wherein performing the NMR measurement comprises performing atleast one of 1H NMR measurements and 19F NMR measurements; and derivingone or more properties of the set of core samples based on the NMRmeasurements at the downhole fluid saturation state and the NMRmeasurements at the reduced fluid pressure.
 8. A system comprising: acoring tool; a pressurized nuclear magnetic resonance (NMR) core holdercoupled to the coring tool, wherein the pressurized NMR core holdercomprises, a housing capable of containing downhole conditions, one ormore NMR coils, and a core chamber containing a fluid comprising aperfluorocarbon; a control system connected to the pressurized NMR coreholder; and a computer-readable medium having instructions storedthereon that are executable by the control system to cause the systemto, collect into the core chamber a set of one or more core samples froma subterranean formation with the coring tool, retrieve the pressurizedNMR core holder from the subterranean formation where the set of coresamples is at a downhole fluid saturation state, perform NMRmeasurements on the set of core samples in the pressurized NMR coreholder at the downhole fluid saturation state, wherein the instructionsto perform NMR measurements comprise instructions to perform at leastone of 1H NMR measurements and 19F NMR measurements, and derive one ormore properties of the set of core samples based on the NMRmeasurements.
 9. The system of claim 8, wherein the fluid furthercomprises one or more of a viscosifier and a weighting agent.
 10. Thesystem of claim 9, wherein the fluid further comprises a viscosifierthat comprises a perfluoropolymer.
 11. The system of claim 8, whereinthe instructions to derive the one or more properties of the set of coresamples comprises instructions to: calibrate the 1H NMR measurements toa 1H NMR measurement of water to produce calibrated 1H NMR measurements;and produce a calibrated 1H image of the calibrated 1H NMR measurements,wherein the instructions to derive one or more properties of the set ofcore samples are based on the calibrated 1H image.
 12. The system ofclaim 8, wherein the instructions to derive the one or more propertiesof the set of core samples comprises instructions to: calibrate the 19FNMR measurements to a 19F NMR measurement of a fluorine-containing fluidto produce calibrated 19F NMR measurements; and produce a calibrated 19Fimage of the calibrated 19F NMR measurements, wherein the instructionsto derive one or more properties of the set of core samples are based onthe calibrated 19F image.
 13. The system of claim 8, wherein the one ormore properties of the set of core samples is selected from the groupconsisting of porosity, movable and non-movable fluids, hydrocarbonfluid types and saturation, wettability, organic content, pore structureincluding pore size distribution, permeability, and fracture and poreconnectivity.
 14. The system of claim 8, further comprising instructionsto: reduce a fluid pressure in the pressurized NMR core holder afterperforming the NMR measurements on the set of core samples in thepressurized NMR core holder at the downhole fluid saturation state;perform NMR measurements on the set of core samples in the pressurizedNMR core holder at the reduced fluid pressure, wherein the instructionsto perform NMR measurements comprise instructions to perform at leastone of 1H NMR measurements and 19F NMR measurements; and derive one ormore properties of the set of core samples based on the NMR measurementsat the downhole fluid saturation state and the NMR measurements at thereduced fluid pressure.
 15. A non-transitory, computer-readable mediumhaving instructions stored thereon that are executable by a computingdevice to perform operations comprising: collecting a set of coresamples from a subterranean formation with a coring tool coupled to apressurized nuclear magnetic resonance (NMR) core holder; placing theset of core samples in the pressurized NMR core holder comprising one ormore NMR coils and containing a fluid comprising a perfluorocarbon;retrieving the pressurized NMR core holder from the subterraneanformation where the set of core samples is at a downhole fluidsaturation state; performing NMR measurements on the set of core samplesin the pressurized NMR core holder at the downhole fluid saturationstate, wherein performing the NMR measurements comprises performing atleast one of 1H NMR measurements and 19F NMR measurements; and derivingone or more properties of the set of core samples based on the NMRmeasurements.
 16. The non-transitory, computer-readable medium of claim15, wherein the fluid comprises one or more of a viscosifier and aweighting agent.
 17. The non-transitory, computer-readable medium ofclaim 16, wherein the fluid further comprises a viscosifier thatcomprises a perfluoropolymer.
 18. The non-transitory, computer-readablemedium of claim 15, wherein the instructions for deriving the one ormore properties of the set of core samples comprise instructions toperform operations comprising: calibrating the 1H NMR measurements to a1H NMR measurement of water to produce calibrated 1H NMR measurements;and producing a calibrated 1H image of the calibrated 1H NMRmeasurements, wherein the instructions to perform operations comprisingderiving one or more properties of the set of core samples are based onthe calibrated 1H image.
 19. The non-transitory, computer-readablemedium of claim 15, wherein the instructions for deriving the one ormore properties of the set of core samples comprise instructions toperform operations comprising: calibrating the 19F NMR measurements to a19F NMR measurement of a fluorine-containing fluid to produce calibrated19F NMR measurements; and producing a calibrated 19F image of thecalibrated 19F NMR measurements, wherein the instructions to performoperations comprising deriving one or more properties of the set of coresamples are based on the calibrated 19F image.
 20. The non-transitory,computer-readable medium of claim 15, further comprising instructions toperform operations comprising: reducing a fluid pressure in thepressurized NMR core holder after performing the NMR measurements on theset of core samples in the pressurized NMR core holder at the downholefluid saturation state; performing NMR measurements on the set of coresamples in the pressurized NMR core holder at the reduced fluidpressure, wherein performing the NMR measurements comprises performingat least one of 1H NMR measurements and 19F NMR measurements; andderiving one or more properties of the set of core samples based on NMRmeasurements at the downhole fluid saturation state and the NMRmeasurements at the reduced fluid pressure.